The present invention relates to a milling drum, in particular a fine milling drum of a road working machine, and a method for manufacturing the same. More particularly it relates to a tool mounting device adapted to be mounted to the surface of a milling drum.
Scarifiers or cold planers equipped with a milling drum are used for removing soil surfaces, in particular asphalted road surfaces. Tools or picks supported on a surface of the milling drum come into contact with the asphalted surface to be removed during rotation of the milling drum. Depending on the particular choice and on the arrangement of the tools on the surface of the milling drum, the road working machine is adapted to either break up the asphalted surface or to grind it to remove only a damaged layer of the surface. For the latter operation, so called fine milling drums are utilized which are adapted to remove a predetermined thickness of the asphalted surface and to simultaneously finish it so it may remain like it is, or to smooth it for a later finishing operation, e.g. paving a new asphalt layer. To this end, the tools have to be densely and accurately arranged on the milling drum surface. In particular, tip portions of the tools which come into contact with the asphalted surface to grind it off, have to be located at a predetermined uniform distance spaced from the milling drum surface and also positioned at a predetermined angle to the circumferential and axial directions of the milling drum.
The tools supported on the milling drum get worn quickly during operation and have to be serviced or exchanged frequently. To this end, it is known to provide tool mounting devices connected to the surface of the milling drum by welding. The tool mounting devices usually comprise a tool mounting portion adapted to releasably hold a tool and a drum connection portion which is fixed to the milling drum surface by welding. One example of such a device is disclosed in U.S. Pat. No. 4,650,254 issued Mar. 17, 1987, which shows a bit or tool holder having an integral base part arranged to be welded front and rear to a curved milling drum. The tools are spaced apart to provide clearance to reduce dust in mining operations.
For fine milling drums, the tool mounting devices may be provided as an integral part having a base block portion to be welded to the drum surface. For example, one known technique is to weld a toolholder or box adapted to accomodate a milling tool to a base block and then weld the base block to the surface of the milling drum. These types of milling drums are also referred to as the xe2x80x9cwelded box typexe2x80x9d milling drums. Inasmuch the tool mounting devices, i.e. their base blocks, have to be densely arranged on the surface, it is necessary to completely weld each individual base block before a next adjacent base block may be attached to the milling drum surface because the previously attached base block can not be reached by any welding tool afterwards.
The present invention is directed to solve this and other problems of the above described prior art.
In accordance with one aspect of the invention, a tool mounting device for a milling drum is disclosed that includes at least one pedestal portion adapted to be welded to a surface of the milling drum and having a first extension in a first axial direction of the milling drum from a first longitudinal side surface of the tool mounting device. The pedestal portion is further adapted to engage the surface of the milling drum along essentially the length of the tool mounting device in a circumferential direction of the milling drum. The pedestal portion provides working space for a tool such as a welding tool and, thus, facilitates finish of a weld seam between a tool mounting device and the surface of the milling drum although, in its vicinity, other tool mounting devices are already arranged on the milling drum surface.
In accordance with another aspect of the invention, a method is disclosed for manufacturing a milling drum, in particular a fine milling drum. The method includes the steps of providing tool mounting devices including at least one pedestal portion adapted to be welded to a surface of the milling drum, said pedestal portion having first and second extensions in opposite axial directions of the milling drum from first and second longitudinal side surfaces of the tool mounting devices, said first and second extensions being adapted to engage the surface of the milling drum along essentially the length of the tool mounting devices in a circumferential direction of the milling drum. In a subsequent step the tool mounting devices are arranged in abutting engagement in a circumferential direction of the milling drum and in a manner to form a welding channel by means of the pedestal portions of respective tool mounting devices adjacent in the axial direction of the milling drum. In a following step, the tool mounting devices are welded to the surface of the milling drum along the welding channel formed by said pedestal portions.